[NetworkManager] blacklisting auto dhcp interfaces in gutsy

Scott James Remnant scott at canonical.com
Mon Sep 10 12:19:00 BST 2007

On Mon, 2007-09-10 at 12:05 +0100, Matt Zimmerman wrote:

> On Mon, Sep 10, 2007 at 12:38:57PM +0200, Alexander Sack wrote:
> > On Mon, Sep 10, 2007 at 10:23:06AM +0100, Matt Zimmerman wrote:
> > > On Mon, Sep 10, 2007 at 10:23:42AM +0200, Alexander Sack wrote:
> > > > On Fri, Sep 07, 2007 at 06:25:24PM +0100, Matt Zimmerman wrote:
> > > > > I'm afraid I'm not up to speed on the technical issues involved here, but
> > > > > the proposed change in behaviour would be a regression for users.  If I
> > > > > understand correctly, folks who installed 7.04 and are happily using
> > > > > network-manager (with the default 'auto dhcp' entries in /e/n/interfaces)
> > > > > would suddenly see it stop working.
> > > > > 
> > > > 
> > > > Yes, if we don't provide an upgrade path to correct this, those
> > > > users will suddenly see it stop working. However, there are also
> > > > things to win: For instance you finally will be able to go to network
> > > > admin in gnome, configure your connection as dhcp and just use that
> > > > without network-manager getting in your way. Currently your only
> > > > choice to use the auto dhcp /e/n/i feature is to purge
> > > > network-manager ... which can't be the right answer imo.
> > > 
Actually, you should also be able to do something like this:

  auto eth0
  iface eth0 inet dhcp

It doesn't matter what the extra bit is, as long as it's there; note
that NM will ignore any stanza more complicated than the usual two

This is there so that NM ignores things like:

  auto eth1
  iface eth1 inet dhcp
    wpa-essid blah
    wpa-key foowibble

Since that's a fixed detail anyway, but can be used for the "don't use
NM with this interface" edge-case.

Long term, it's probably best for NM to parse /e/n/i and actually use it
properly; e.g. treat values there as hard-coded.  So if you had a
wireless interface defined in /e/n/i like so:

  auto eth1
  iface eth1 inet static
    wpa-essid blah
    wpa-key foowibble

Then NM would just ensure that the interface, when up, had those
details.  And would obviously check ifstate, etc.

Then it wouldn't matter whether NM was used or not, because the effect
would be identical to using /e/n/i itself.

That would require more improvements to NM to make it inherit existing
interface configuration, rather than blatting it on startup.

A fair amount of work, really.

> >  3. advance users that want a mix of both (wired through /e/n/i auto
> >  dhcp, but wireless still managed through NM); they don't have the
> >  option to purge network manager and thus only have the /e/n/i
> >  workaround as a fallback.
> Again, in use case language:
> Alison installs an Ubuntu laptop, but she really wants her primary
> ethernet
> interface to be nailed up and not subject to Network Manager's whims.
> She
> adds the interface to /etc/network/interfaces, and Network Manager
> then
> ignores that interface, still allowing her to use it for wireless
> connections when traveling.
This would require improvements to NM and the policy agent to allow
interfaces to be simultaneously up.  It's possible to do, the "only one
up at a time" is simply a policy decision in nm-applet; not a hard

(Obviously you don't want to break the current behaviour for people that
like it "I plug a cable into my laptop, and it automatically uses that
instead of the wireless \o/")

Scott James Remnant
Ubuntu Development Manager
scott at canonical.com
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